Method of preparing lubricating oil stocks from asphalt-containing crude petroleum ois



Patented Dec. 27 1938 UNITED STATES PATENT OFFICE METHOD OF PREPARING LUBRICATING OIL STOCKS FROM ASPHALT-CONTAINING CRUDE PETROLEUM OILS Ernest W. Thiele, and Bernard Ginsberg, Chicago, Ill., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Application May 28, 1936, Serial No. 82,252

3 Claims. (Cl. 1961) stock presents a special problem in the refinery because the deasphalting process has so altered the physical properties of the finished oil that it cannot be used in the hundreds of formulae which employ lubricating stocks of this character. The drop size of this stock is so altered that the oil can no longer meet the specifications for steam cylinder lubrication. The pour test is higher than that of similar oils produced by acid treating. Likewise, the color, cast, acidity and carbon residue are all materially changed. The object of our invention is to modify the characteristics of deasphalted lube stock so that it will retain its advantages over acid treated stock, and so that it may be substituted for the acid treated stock in steam cylinder oils, greases and other compounds.

A further object is to provide a means for so modifying the characteristics of a steam refined oil produced by propane deasphalting that it will be unnecessary to blend said stock with bright stock in order to meet market and manufacturing specifications. Heretofore it has been customary to blend about 30% of bright stock with steam refined stock in order to obtain an oil of desired physical characteristics, this is no longer necessary.

We have discovered that by adding from about to of cracked tar residues, we can materially improve the pour test, improve the drop size characteristics and meet all requirements of the formulae which heretofore employed the acid treated lubricating stocks. We have found that for most purposes /270 of this tar residue is sufiicient to make the deasphalted oil meet all previous tests and at the same time we have found that the oil with the added material is stable against oxidation, has better color than prior acid treated stocks, and has far less tendency to form carbon. The invention will be more clearly understood from the following detailed description:

Our invention will be described in the manufacture of steam refined stock from Mid-Continent crude which has been distilled in a pipe still 1 with steam or vacuum to a bottoms having a Saybolt viscosity of 400 seconds at 210 F. This reduced crude is then deasphalted with about three volumes of propane at a temperature of about F. to F. and a pressure of about 200 to 400 pounds per square inch to give a deasphalted oil of about the following characteristics:

Viscosity at 210 F.-197 to 207 seconds Saybolt.

. Flash-535 to 545 F.

Color-less than 5-6 N. P. A. (double dilute). Yield85%. Solid point-90" F. to 85 F.

For most purposes it is necessary that such steam refined stock have a solid test of about 65 F. to 40 F. Pour point depressors of the type. prepared by condensing chlorinated wax with aluminum chloride are not effective to produce the desired results even when used in amounts. up to 4%. Asphaltic residuums added to the oil in small amounts likewise prove relatively ineffective. We have discovered, however, that certain cracked tars are remarkably and unexpectedly effective, particularly the tars produced as a residuum by the distillation of the pressure tar produced by the cracking of petroleum oils to form gasoline. Such reduced pressure tars are efiective not only for lowering the cold test of the steam refined stock, but for improving other physical properties.

A preferred example of our reduced pressure 35 tar is the heavy residuum resulting from the distillation of light fractions from a pressure tar which is obtained from the cracking of gas oil to form gasoline at pressures of about 300 to 400 pounds per square inch and temperatures of about 850 to 925 F. The reduced pressure tar has the following specifications:

Melting point (by Ball and Ring method) to F. 45 Penetration at 77 F.-'8 to 14. Specific gravity at 60 F.1.06+. Solubility in carbon disulfide-99+%.

Such reduced pressure tar is sold on the market as hard Stanolite. In addition to the above 50 characteristics the reducedpressure tar which we employ is characterized by a greater susceptibility to temperature change than is displayed by most asphaltic materials.

We have discovered that when of reduced 55 pressure tar, as above described, is added to the propane deasphalted steam refined stock its solid point is lowered to about 71 F. to 45 F. The use of 1 of this tar residuum lowers the solid point to about 63 F. to 38 F. The addition of the reduced pressure tar has very little effect on the flash test which remains at least 530 F. The addition of about 1% of this material increases the viscosity from about 194 to 198 seconds Saybolt at 210 F. The propane deasphalted stock with 1 /2% of added pressure tar residuum has a true color of 2020 and an N. P. A. color of 5 (double dilute) as compared with the conventional acid treated steam refined stocks which have a true color of 2370 and an N. P. A. color of 5-6 (double dilute). The stability against oxidation (indicated by color after 24 hours at 210 F.) shows that the deasphalted oil with added reduced cracked tar is more stable than the acid treated stocks heretofore employed, the deasphalted oil having a true color after the test period of 2370 as compared with the acid treated stock which has a true color after a similar test period of 2950.

An important result accomplished by the use of reduced pressure tar in deasphalted lub stock is the effect on drop size which is obtained thereby. The deasphalted stock has a drop size of about .15 cm. dia., which is larger than desirable when the stock is used for cylinder oil to lubricate steam cylinders. We have found that 1% of the reduced pressure tar lowers the drop size to about .12 cm., and that by using 2% of the added reduced tar the added reduced oil has a drop size of about .10 cm. The drop size may be further modified by the addition of small amounts of sperm oil.

The addition of reduced pressure tar as hereinabove described makes the oil smoother, i. e., less grainy (from wax crystals) when viewed by transmitted light in a thin film on glass. This smoothness may be further improved by the addition of a small amount of bright stock but we have found that our steam refined stock meets all specifications without the use of added bright stock.

We claim:

1. In the method of preparing lubricating oil stocks from mixed base crude petroleum oils by distilling said oils under non-cracking conditions to obtain a viscous heavy residue, deasphalting said residue with propane at about 100 F. to 115 F., and separating propane from the deasphalted oil, the improvement which consists of adding to said deasphalted oil about /4% to 2% of a reduced pressure tar obtained from the cracking of gas oil at pressures of about 300 to 400 pounds per square inch and temperatures of about 850 to 925 F., said pressure tar having a specific gravity at F. of at least 1.0.

2. In the method of preparing lubricating oil stocks from asphalt-containing crude petroleum oils by distilling said oils under non-cracking conditions to leave a residue having a Saybolt viscosity of about 400 seconds at 210 F. and deasphalting said residue with about 3 volumes of propane at a temperature of about F. to give a deasphalted oil having a flash point of about 535 F. and a viscosity of about 200 seconds Saybolt at 210 F., the improvement of adding to said deasphalted oil about /4% to 2% of the heavy residuum resulting from the distillation of light fractions from a pressure tar obtained from the cracking of gas oil at pressures of about 300 to 400 pounds per square inch and temperatures of about 850 to 925 F.

3. The method of improving the properties of a steam-refined lubricating oil stock which has been deasphalted with propane at about 100 F. to F., and which has, in the deasphalting step, lost certain components which are desirable in the finished lubricating oil, which method consists essentially of adding to said deasphalted steam-refined stock about /4% to 2% of a reduced pressure tar having about the following specifications:

Melting point (by ball and ring method)about to F. Penetration at 77 F.about 8 to 14. Specific gravity at 60 F.about 1.06. Solubility in carbon -disulfideat least 99%.

ERNEST W. THIELE. BERNARD GINSBERG. 

